comparing water pickups

[sundog]

I just read "Watercooling an RC Boat" by Paul Pachmayer here on OSE http://www.offshoreelectrics.com/inf...tercooling.php and he ends his article with this statement "The last thing I do is make a "thermostat" for the cooling system. Just like in a car you don't want the water going through the system so fast that it doesn't have a chance to remove heat." Then he goes on to say he makes an orifice to slow the flow down.

Paul was no doubt just repeating something he heard, perhaps from the gas boaters (inadvertently perpetuating the myth). In a car, the thermostat allows the engine to warm up to optimum operating temperature, before allowing the coolant to flow again. The cap keeps the system pressurized, allowing it to reach a higher temp without boiling. Otherwise, if the water continually flowed, it would stay so cool, it would never reach that optimum temperature, and efficiency would suffer.

In a FE boat motor (as with lipo batteries), that optimum temp is much lower - closer to room temperature. Unless you're running in ice water, you want to remove as much of the heat as possible. The faster you can move water past an object the more heat it can remove. You can call it the Sundog Factor.

[mtbenjamin77]

I just read "Watercooling an RC Boat" by Paul Pachmayer here on OSE http://www.offshoreelectrics.com/inf...tercooling.php and he ends his article with this statement "The last thing I do is make a "thermostat" for the cooling system. Just like in a car you don't want the water going through the system so fast that it doesn't have a chance to remove heat." Then he goes on to say he makes an orifice to slow the flow down.

Paul was no doubt just repeating something he heard, perhaps from the gas boaters (inadvertently perpetuating the myth). In a car, the thermostat allows the engine to warm up to optimum operating temperature, before allowing the coolant to flow again. The cap keeps the system pressurized, allowing it to reach a higher temp without boiling. Otherwise, if the water continually flowed, it would stay so cool, it would never reach that optimum temperature, and efficiency would suffer.

In a FE boat motor (as with lipo batteries), that optimum temp is much lower - closer to room temperature. Unless you're running in ice water, you want to remove as much of the heat as possible. The faster you can move water past an object the more heat it can remove. You can call it the Sundog Factor.

It's simple, the cooler the water, the faster it absorbs heat. If your motor is 120 degrees and you try to cool it with 120 degree water, the water won't be able to absorb any more heat.

[Heaving Earth]

I just read "Watercooling an RC Boat" by Paul Pachmayer here on OSE http://www.offshoreelectrics.com/inf...tercooling.php and he ends his article with this statement "The last thing I do is make a "thermostat" for the cooling system. Just like in a car you don't want the water going through the system so fast that it doesn't have a chance to remove heat." Then he goes on to say he makes an orifice to slow the flow down.

Paul was no doubt just repeating something he heard, perhaps from the gas boaters (inadvertently perpetuating the myth). In a car, the thermostat allows the engine to warm up to optimum operating temperature, before allowing the coolant to flow again. The cap keeps the system pressurized, allowing it to reach a higher temp without boiling. Otherwise, if the water continually flowed, it would stay so cool, it would never reach that optimum temperature, and efficiency would suffer.

In a FE boat motor (as with lipo batteries), that optimum temp is much lower - closer to room temperature. Unless you're running in ice water, you want to remove as much of the heat as possible. The faster you can move water past an object the more heat it can remove. You can call it the Sundog Factor.

Absolutely sundog. Obviously Paul has no idea what a thermostat on a car actually does. Lol

[sundog]

Best location for flush mounted pickups

Now back to the original question - the best location for flush mounted pickups. As I stated earlier, if located at the transom (with surface piercing props), the transom may lift free of the water when the hull is at high speeds, reducing or even stopping the flow of water. In a modern stepped hull, the highest velocity can be obtained at the bottom rear of the first step in the hull (see attached pics). And as Kingwrench alluded to, even flush mount pickups cause a certain amount of drag. But you can use this to your advantage, for instance by installing it in the port sponson, it can help reduce or eliminate torque roll in a particular hull design. If you 'balance' the system by putting one in each sponson, it may be better to run one to the esc and the other to the motor, rather than combining them with a 'Y' because water takes the path of least resistance, and it could possibly cause a loss of pressure if one sponson lifts free of the water. I realise this all runs against 'old school' lessons gleaned from bygone days of non-stepped hulls, but is worthy of consideration with modern three point, and stepped surface-piercing hull designs. Feel free to include your own observations and ideas - but please don't include any "because that's the way it has always been done" statements (you all know who I'm talking about), as (I think you'll agree) that serves no purpose other than to make the 'teacher' appear smarter and belittle the student.

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[ray schrauwen]

I agree more is better. as for equalizing the flow using a Y, a simple test procedure is all that's needed. A water bottle with a fitting installed on the cap.. fill with water and hook to the hose at the rudder let gravity pull the water throught hte system and which ever side has a weaker stream flowing out of the outlet just shorten the line. but again your splitting hairs. if the left side outlet has a 3" stream of water flowing out and the right side has a 2" stream that's not enough variance to make any difference in temps. The only thing I'd worry about is if one side had nothing coming out. Also when installing the Y it needs to be placed as close the the water source as possible kinda like this..............

[ATTACH=CONFIG]94941[/ATTACH]

That's a cool picture! Thanks! You run that puppy yet??

[ray schrauwen]

Paul may have iterated this way back in the day of NIMH running boats that were slower than today's Lipo missles. If a boat is going slower with NIMH tech it may not flow enough water to cool sufficiently, therefore the restriction or thermostat.???? Just tossing it out there!

I just read "Watercooling an RC Boat" by Paul Pachmayer here on OSE http://www.offshoreelectrics.com/inf...tercooling.php and he ends his article with this statement "The last thing I do is make a "thermostat" for the cooling system. Just like in a car you don't want the water going through the system so fast that it doesn't have a chance to remove heat." Then he goes on to say he makes an orifice to slow the flow down.

Paul was no doubt just repeating something he heard, perhaps from the gas boaters (inadvertently perpetuating the myth). In a car, the thermostat allows the engine to warm up to optimum operating temperature, before allowing the coolant to flow again. The cap keeps the system pressurized, allowing it to reach a higher temp without boiling. Otherwise, if the water continually flowed, it would stay so cool, it would never reach that optimum temperature, and efficiency would suffer.

In a FE boat motor (as with lipo batteries), that optimum temp is much lower - closer to room temperature. Unless you're running in ice water, you want to remove as much of the heat as possible. The faster you can move water past an object the more heat it can remove. You can call it the Sundog Factor.

[sundog]

Paul may have iterated this way back in the day of NIMH running boats that were slower than today's Lipo missles. If a boat is going slower with NIMH tech it may not flow enough water to cool sufficiently, therefore the restriction or thermostat.???? Just tossing it out there!

WT? I am just not very good at explaining things, that's all there is to it. If the flow was insufficient to cool it, you wouldn't want to restrict it more. No, I think it was a holdoff from the gasser days - maybe you need to allow the engine to come up to temperature for best performance (any gassers out there?).

The 29" Tenshock is a recent aquisition, I've not had it in the water yet, but have been busy changing/modifying things to suit me. The water outlet was located front and center for convenience and to keep tubing length to a minimum. If you look closely you'll see the electrical tape over the previous location hole. It would spray water over the boat while running (I had seen a video of it running previously). Since I use a 2.4ghz (microwave) transmitter and water spray/mist has been known to cause signal loss, I relocated the outlet to the top deck well behind the antenna. The rudder was a kick-back type but was drilled incorrectly, not allowing it to tilt. The rudder has a water port, but was not being used, so I tapped/plugged the hole on top to prevent unnecessary drag. Shortened the lengthy esc wires and installed 8mm bullets instead of the Deans and 'Y' adapter (set up for 6S). The drain slot in the step (self righting design) is a nice touch and carbon fiber just looks sexy to me. Am getting anxious to run it now.

[mtbenjamin77]

WT? I am just not very good at explaining things, that's all there is to it. If the flow was insufficient to cool it, you wouldn't want to restrict it more. No, I think it was a holdoff from the gasser days - maybe you need to allow the engine to come up to temperature for best performance (any gassers out there?).

That is exactly the difference between IC and FE. FE is much more efficient at lower temperature, IC engine need to acheive and maintain a constant temperature to maintain efficiency, therefore you restrict the flow of coolant with a thermostat to bring the engine up to temp. I.E less coolant means more heat

[Heaving Earth]

Paul may have iterated this way back in the day of NIMH running boats that were slower than today's Lipo missles. If a boat is going slower with NIMH tech it may not flow enough water to cool sufficiently, therefore the restriction or thermostat.???? Just tossing it out there!

The fact is, Paul has no idea what a thermostat on a car does based on his statement period. Regardless of the situation or times, he thinks a thermostat slows the flow so it has time to extract heat! Nonsense. Ose should get with the times and remove that rubbish.

[Cooper]

One of the annologies I used about water cooling- take your hot motor, drip water over it and see how long it takes to cool, now take the same motor, heated up again, and throw it in the lake, now which one do you think will cool to the ambient temperature of the lake water? Faster????? There is no other comparable cooling method used like our boats, not cars not even inboards that use the water they run in for cooling. Electronics function better at lower temps (lipos are about the only exception-but they aren't really electronics) it's really the laws of physics, no need for documented proof of this so basic law, EVERYTHING is dissipating heat to its cooler surrounding. Or I should say that heat is always trying to dissipate. This thermo-transfer will only stop when absolute zero is reached ( when all molecular movement stops). Yep that's the truth and no deviation, if you don't agree with that then you don't have the basic concept of our physical world. Don't want to sound harsh but if we all can build a better mousetrap by starting with known facts we will likely achieve favorable results sooner. And warm water will not freeze faster than cold water!!!!!

[Cooper]

Oh and while so,done else stated the idea of a scuffed bottom being faster, nope. Golf balls are about the only thing made that has an irregular surface for improved air dynamics. The dimples actually create air voids from a otherwise non dynamic stagnate (dead ball). Originally the flight of a golf ball was non rotational and the dimples helped tremendously with length and trajectory of the ball. Our boats and all other over 50mph in the air and really any speed in water surfaces will be extremely more efficient in displacing the water by having a smooth surface. Again this is proven physics and fundamental text book stuff , not to be debated. Now as far as props scuffed surface has been proven to benefit with racing, but only on quick acceleration, not top speed. And back to the op, guess it really depends on the water pick up, all have pros and cons. I personally think the rudder pick ups deliver the most water.

[ray schrauwen]

It's nice to have a reminder, tks

[keithbradley]

if you don't agree with that then you don't have the basic concept of our physical world.

These topics always frustrate me because It's hard to be nice and still debate this type of stuff. I understand that not everyone has a basic understanding of physics, but for those who don't, it would only make sense to defer to those who do. The only people who debate this subject are people that have absolutely zero understanding of the very subject they are talking about...it's impossible to understand energy transfer in it's simplest form and still believe that slower (warmer) water removes more energy. I question how these people think their batteries work.

[egneg]

Ok ... you slower the flow guys answer this. Why does a cars radiator have several tubes and fins (and a fan with a T-stat)?

Answer: To maximize surface area and water flow (and air flow at slow speeds) to cool the water as quick as possible. IC engines were designed to operate in a given temp range for proper fuel/air mixture being taken in. To hot and you have vapor lock - to cold and you don't have proper fuel atomization.

This is not true with electric motors and ESC's. With FE motors that have case cooling and ESC's you want maximum flow. As water temps on a lake are in a fairly narrow range and very close to what the motor and ESC temps should be.

I am done now.

[sundog]

These topics always frustrate me because It's hard to be nice and still debate this type of stuff.

Keith, I know you have a business where it's important to be 'nice', but I gave up nice a while back when I realized the geezers were passing on bad info. Especially when one particular know-it-all was trying his best to make me look the fool when I would introduce new concepts and ideas. Kinda made me think of why would the racers give you quality info when they know you might be competing against them some day? So now I'll light into it when I see bad info. Especially when I hear "because it's always been done that way". You know how much I love that statement. If you are not open to new concepts and ideas, you are doomed to the back of the pack (and to receive a verbal thrashing from yours truly). It seems I am not always smart enough to keep my mouth shut, or fingers still.